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The following information
will be useful when making your whiriligigs :- |
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Cams :-
A cam is a specially shaped piece of metal
or plastic. The edge, or profile of the
cam guides the motion of the follower. Cams are
mechanisms which can be used to change one type
of motion to another; the input motion may be
rotary or reciprocating. This is converted to
a output motion of the follower. |
The animation to the right
shows a different kind of cam called a pear cam.
This has a different kind of motion to the square
cam shown above. It has a smoother motion because
it has a continuous curved shape - the motion
is transmitted to the follower without any sudden
jerks. This is the kind of cam you will need to
use for the whirligigs because it will produce
a nice smooth motion for good movement t of the
models. |
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This is the Lazy Susan bearing.
Like any other kind of bearing it requires ball
bearings to make it move correctly. These are
used on the whirligigs because they produce a
very smooth motion for them to spin around on.
Note the size of the bearing compared to an average
calculator. This is the size you need ( 4"
square) |
There are two holes on every
corner of a Lazy Susan bearing. There are
used to attach the model to the wood - in this
case a whirligig - and post it will be attached
too. Notice the two sizes of holes. One is used
for nails (the smaller hole) and the other is
used for screws (the larger hole). I recommend
the use of screws for this model as you have a
less chance of splitting the wood. They look nicer
too! |
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This picture shows how a
whirligig is attached to the base of a
post. There are two square pieces of MDF used
( 5" square"). One is attached to the
top and bottom of the Lazy Susan - the top piece
then holds the pin ( small dowel) to be inserted
into the rotational point of the model. The bottom
MDF square is then glued to the post. You model
should then be able to spin and turn in the wind
correctly ! |
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